<!DOCTYPE html>
<html lang="cn">

<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>

<body>
    <h1>Start</h1>
    
<script type="text/javascript">
    /*
    
    基础
    
    */
    alert("hello world");
    const call = "你好" // 申明一个常量
    var HelloQuestion = "你好吗？"
    alert(call); alert(HelloQuestion)
    document.write('<h2>yeah</h2>')
    console.log('haha')
    function callit(){   //最简单的func
        
        alert(3);alert(2);alert(1)
    }
    callit()
</script>


<script type="text/javascript">
// js是弱引用类型
var foo  = 5
var foo = "我是弱引用类型"
console.log(foo)
console.log(foo,typeof foo)
console.log(1,typeof 1)
console.log(undefined,typeof undefined)
console.log(true,typeof true,typeof typeof true)
</script>
</body>

</html>